Droplet actuator fabrication apparatus, systems, and related methods

ABSTRACT

Example methods, apparatus, systems for droplet actuator fabrication are disclosed. An example non-transitory computer readable medium includes instructions that, when executed, cause at least one processor to at least control movement of a laser to cause the laser to etch an electrode pattern in a first substrate, the electrode pattern including a first set of electrodes, a second set of electrodes, and a third set of electrodes; control a printer driver to cause a hydrophobic material and a dielectric material to be applied to the second set of electrodes and not the first set of electrodes via a printer; control a bonding driver to cause a gap to be defined between the first substrate and a second substrate; and control a dicing driver to cause a portion the first substrate and a portion of the second substrate to be cut into a droplet actuator.

RELATED APPLICATIONS

This patent arises from a continuation of U.S. patent application Ser.No. 14/687,398, which was filed on Apr. 15, 2015. U.S. patentapplication Ser. No. 14/687,398 claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/980,422, filed Apr.16, 2014. U.S. patent application Ser. No. 14/687,398 and U.S.Provisional Patent Application No. 61/980,422 are hereby incorporated byreference in their entireties. Priority to U.S. patent application Ser.No. 14/687,398 and U.S. Provisional Patent Application No. 61/980,422 ishereby claimed.

FIELD OF THE DISCLOSURE

This disclosure relates generally to electrode arrays, and, moreparticularly, to droplet actuator fabrication apparatus, systems, andrelated methods.

BACKGROUND

Droplet actuators are used in a variety of microfluidic operations formanipulating and analyzing discrete volumes of fluid. Droplet actuatorsinclude two plates separated by a gap, with at least one of the platescontaining an array of electrodes coated with a hydrophobic and/ordielectric material. Fabricating drop actuators involves creating theelectrode array, which can require high production costs in terms oftime and pricing to define the electrode array without sacrificingtechnical performance qualities of the electrodes of the array.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a first example assembly for creating a basesubstrate of an example droplet actuator.

FIG. 2A is a top view of an example electrode pattern on the examplebase substrate created via the first example assembly of FIG. 1. FIG. 2Bis a top view of a portion of the example electrode pattern of FIG. 2Acreated via broad field laser ablation.

FIG. 2C is a top view of a portion of the example electrode pattern ofFIG. 2A created using laser ablation scribing techniques. FIG. 2D is across-sectional view of the example base substrate including a pluralityof electrode arrays, taken along the 1-1 line of FIG. 2A. FIG. 2E is across-sectional view of the electrode pattern taken along the 2-2 lineof FIG. 2A.

FIG. 3 is a diagram of a second example assembly for creating a topsubstrate of an example droplet actuator.

FIG. 4 is a diagram of a third example assembly for merging the examplebase substrate created via the first example assembly of FIG. 1 with theexample top substrate created via the second example assembly of FIG. 3.

FIG. 5 is a block diagram of an example processing system for the firstexample assembly of FIG. 1, the second example assembly of FIG. 3, andthe third example assembly of FIG. 4.

FIG. 6 is a flow diagram of an example method that can be used toimplement the examples disclosed herein.

FIG. 7 is a diagram of a processor platform for use with the examplesdisclosed herein.

The figures are not to scale. Instead, to clarify multiple layers andregions, the thickness of the layers may be enlarged in the drawings.Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts. As used in this patent, stating that any part (e.g., alayer, film, area, or plate) is in any way positioned on (e.g.,positioned on, located on, disposed on, or formed on, etc.) anotherpart, means that the referenced part is either in contact with the otherpart, or that the referenced part is above the other part with one ormore intermediate part(s) located therebetween. Stating that any part isin contact with another part means that there is no intermediate partbetween the two parts.

DETAILED DESCRIPTION

Methods, systems, and apparatus involving fabrication of dropletactuators are disclosed herein. Droplet actuators are used inmicrofluidic analysis, and, in particular, are used in the field ofdroplet-based, or digital, microfluidics. Droplet actuators include twosurfaces separated by a gap. At least one of the surfaces includes anelectrode array that is coated or insulated by a hydrophobic material ora dielectric. A droplet disposed in the gap can be manipulated on thesurface of the hydrophobic and/or dielectric material by selectivelyapplying electrical potentials to electrodes of the electrode array toaffect the wetting properties of the hydrophobic and/or dielectricsurface pursuant to, for example, electrowetting or dielectrophoresisprocesses. Droplets disposed in the gap can include biological fluidsamples such as, for example, blood, plasma, serum, saliva, sweat, etc.Electrical potentials may be used to transfer droplets between adjacentelectrodes of the array, and/or to merge or split droplets as part of avariety of analyses, including for example, DNA sequencing and proteinanalysis.

Fabricating the example droplet actuators disclosed herein includescreating an electrode pattern that includes an electrode array on a basesurface and coating the surface with at least one layer of a materialexhibiting hydrophobic and/or dielectric properties. Producing theexample droplet actuators also includes creating a top substrate, whichmay include a conductive surface coated with a material havinghydrophobic and/or dielectric qualities and joining (e.g., bonding) thetop substrate and the bottom substrate at a spaced apart distance toaccommodate a droplet. The pattern of the electrode array that iscreated on at least the base substrate is based on design qualities ofthe electrodes that affect performance of the droplet actuator, such as,for example, electrical conductivity and electrode spacing. Increasingthe number of electrodes per an area of the substrate provides foraccommodation of differently sized electrodes and greaterinter-digitation of the electrodes in the array. Higher resolution ofthe electrode array results in increased precision of the sizes of thedroplets that are actuated by the droplet actuator and facilitates easeof transfer of the droplets between electrodes.

Known methods and systems for fabricating droplet actuators require acompromise between production efficiencies and quality of the electrodearray. For example, lithographic methods provide for high spatialresolution in defining electrode arrays, but involve slow productiontimes and expensive methodology. For example, lithographic methodsinvolve depositing a photoresist on a substrate to engrave patterns inthe substrate via chemical treatments. Depositing the photoresist mustbe repeated across the substrate to form individual electrode arrays,which increases production times. Also, droplet actuators formed usinglithographic methods require post-processing steps such as cleaning thedroplet actuators to remove the photoresist from the substrate. However,traces of chemicals can remain on the substrate after rinsing and canresult in water marks on the substrate. Further, although lithographicmethods can provide for high spatial resolution of an electrode array,the quality of the lines and gaps of the resulting electrode array canbe poor quality, including rough edges defining the electrode array andrandom (e.g., non-systematic) defects between droplet actuators dueinconsistencies with respect to deposition of the photoresist on thesubstrate.

Attempts to improve production efficiencies include printing electrodeson printed circuit boards. However, although the use of printed circuitboards may provide for faster production of droplet actuators at reducedmaterial costs as compared to lithographic methods, the spatialresolutions of the arrays are sacrificed, which affects the capabilitiesof the droplet actuator in generating and manipulating droplets. Dropletactuator fabrication methodologies involving printed circuit boards canalso require multiple steps to join or adhere one or more of asupporting surface and/or a hydrophobic surface to the printed circuitboard to form the base layer of the droplet actuator.

Disclosed herein are example methods and systems for fabricating dropletactuators using laser ablation as part of a roll-to-roll assembly. Laserablation can define electrode arrays including a plurality of electrodesat fast production speeds without sacrificing electrode quality byremoving materials from a solid substrate via laser beam in a controlledmanner. Technical advantages of electrodes produced via laser ablationinclude increased electrical conductivity as compared to printedelectrodes; a low degree of surface roughness; a low degree of roughnessassociated with the edges defining the electrode features, therebyimproving inter-digitization of the electrodes of the array; and a lowdegree of variation between features of the respective electrodes of thearray. Laser ablation can produce an electrode pattern including linesand gaps measuring from, for example, less than 5 μm to about 10 μm.Further, laser ablation does not require the use of solvents that mightnegatively interfere with the use of the resulting droplet actuators byleaving residues or chemicals that are harmful to the productionenvironment.

The example methods and systems disclosed herein are implemented via aroll-to-roll assembly, which can operate to move a substrate throughvarious stations at high speeds, including, for example, rates of metersper second. Roll-to-roll assemblies facilitate the unwinding of a rolledsubstrate, the advancement of the substrate through the stations, andthe rewinding of the processed substrate into a roll. Thus, a baseand/or top substrate of a droplet actuator may be processed through oneor more of a laser ablation station, a hydrophobic and/or dielectricprinter, and a curing station at a rapid, continuous pace withoutcompromising the technical qualities of the resulting droplet actuator.Further, the disclosed example methods and systems produce a basesubstrate and/or top substrate that do not require further individualassembly with respect to, for example, the electrode array, thehydrophobic and/or dielectric layer, and/or a supporting structuralbase, thereby reducing operation time and costs. Thus, examplesdisclosed herein provide for efficient production of droplet actuatorswithout sacrificing quality of the microfluidic device.

An example method disclosed herein for making a droplet actuatorincludes ablating a first substrate with a laser to form an electrodearray on the first substrate. The example method includes applying atleast one of a hydrophobic or a dielectric material to the electrodearray to form a first treated layer on the first substrate. The examplemethod also includes aligning the first substrate with a secondsubstrate. The second substrate includes a second treated layer. In theexample method, the alignment includes a gap between at least a portionof the first treated layer and at least a portion of the second treatedlayer.

In some examples, the method includes inserting one or more capillarytubes between the first substrate and the second substrate to create thegap.

In some examples, the method includes curing at least one of thehydrophobic material or the dielectric to form the first treated layer.In some examples, curing the hydrophobic material includes exposing theat least one of the hydrophobic or the dielectric material to at leastone of heat or ultraviolet light.

In some examples, ablating the first substrate includes projecting apattern onto a portion of the first substrate via a lens and focusingthe laser on the portion. In such examples, the laser is to penetratethe portion to form the pattern on the portion. Also, in some suchexamples, the pattern comprises a plurality of lines and gaps, the lineshaving a width of about 10 micrometers.

Also, in some examples, ablating the first substrate includes exposing aplurality of portions of the first substrate to the laser in succession.In such examples, the laser is to form the electrode array onto each ofthe plurality of the portions.

In some examples, the method includes coating a first portion of theplurality of portions with the at least one of the hydrophobic or thedielectric material at substantially the same time a second portion ofthe plurality of portions is exposed to the laser.

In some examples, the first substrate includes at least a first portionand a second portion. Each of the first portion and the second portioncomprises a respective electrode array. In such examples, the secondsubstrate includes at least a third portion and a fourth portion. Also,in such examples, aligning the first substrate with the second substrateincludes aligning the first portion and the third portion at a firstspaced apart distance and the second portion and the fourth portion at asecond spaced apart distance. The first spaced apart distance and thesecond spaced apart distance correspond to the gap. In some examples,the method includes dicing the aligned first substrate and the secondsubstrate, wherein the dicing is based on the alignment of the firstportion and the third portion and the second portion and the fourthportion. Also, in some examples, the method includes bonding the firstportion the third portion and the second portion and the fourth portion,respectively, with an adhesive material.

Also disclosed herein is an example system including a plurality ofrollers to drive a first substrate between a plurality of positions. Theexample system includes a laser to penetrate the first substrate whenthe first substrate is in a first position of the plurality ofpositions. The laser to form at least one electrode pattern on the firstsubstrate. The example system includes a printer to apply at least oneof a hydrophobic or a dielectric material to the at least one electrodepattern when the first substrate is in a second position of theplurality of positions. In the example system, the plurality of rollersare to drive the first substrate from the second position to a thirdposition of the plurality of positions. In the third position, the firstsubstrate is to align with a second substrate to form a dropletactuator.

In some examples, the laser is to substantially continuously pulseduring operation of the plurality of rollers and the laser is topenetrate one or more portions of the first substrate during theoperation of the plurality of rollers.

In some examples, the first substrate comprises a first layer and asecond layer. The second layer comprises a conductive material. In someexamples, the first substrate includes a third layer disposed betweenthe first layer and the second layer. The third layer is to adhere thesecond layer to the first layer.

In some examples, the laser is to remove at least a portion of thesecond layer to form the electrode pattern.

In some examples, the second layer is disposed on the first layer in afirst roll. The plurality of rollers are to unwind the first roll todrive the first substrate to the first position. The plurality ofrollers are to drive the first substrate to the third position to form asecond roll. In such examples, the second layer is disposed on the firstlayer in the third position.

Some of the disclosed examples include a splitter to cut the second rollto form at least one microfluidic chip.

Also, in some examples, the printer comprises one or more coatingrollers to apply the at least one of the hydrophobic or the dielectricmaterial to the at least one electrode pattern. In some examples, thecoating rollers are to apply an anti-fouling material to the firstsubstrate.

In some examples, the system further comprises a merger to align thefirst substrate with the second substrate in the third position. In someexamples, the merger comprises two rollers. Also, some of the disclosedexamples include a curing station to cure the at least one of thehydrophobic material or the dielectric material. Some of the disclosedexamples also include a bonding station to bond at least a first portionof the first substrate with at least a first portion of the secondsubstrate. The bonded portions include the at least one electrodepattern.

Also disclosed herein is an example method including patterning anelectrode array on a first sheet using a laser. The example methodincludes applying at least one of a hydrophobic material or a dielectricto the first sheet to create a first treated layer. The example methodincludes applying the at least one of the hydrophobic material or thedielectric to a second sheet to create a second treated layer. Theexample method also includes associating the first sheet and the secondsheet at a spaced apart distance. The first treated layer is aninsulating layer relative to the electrode array and a droplet receivedbetween the first treated layer and the second treated layer.

In some examples, the method includes curing the first treated layer andthe second treated layer.

In some examples, associating the first sheet and the second sheetincludes orienting the second treated layer in a first orientation, thefirst orientation opposite a second orientation of the first treatedlayer and merging the first treated layer and the second treated layerin a substantially parallel configuration. In some examples, merging thefirst sheet and the second sheet includes applying an adhesive materialto at least one of the first sheet or the second sheet and bonding thefirst sheet with the second sheet. In such examples, the bonding is topreserve the spaced apart distance between the first sheet and thesecond sheet.

In some examples, the second sheet comprises a substantially singleelectrode. The second treated layer is to insulate the electrode.

In some examples, the method includes patterning an electrode array onthe second sheet. In some examples, the second sheet includes anon-conductive material.

In some examples, the method includes embossing the first sheet tocreate one or more projections on the first sheet. In such examples, theprojections are to separate the first sheet and the second sheet at thespaced apart distance.

Also disclosed herein is an example apparatus including a non-conductivelayer and a conductive layer. The conductive layer is adhered to thenon-conductive layer. The example apparatus includes an electrodepattern disposed in the conductive layer. The electrode pattern isinsulated by at least one of a hydrophobic or a dielectric material. Inthe example apparatus, at least a portion of the non-conductive layerincludes a feature of the electrode pattern.

In some examples, the feature is an outline of at least a portion of theelectrode pattern. In some examples, the electrode pattern comprises aline and the feature at least partially corresponds to a position of theline in the electrode pattern. Also, in some examples, the feature is atleast one of an indentation or a projection in a surface of the portionof the non-conductive layer.

In some examples, the example apparatus includes an anti-fouling layerdisposed on the electrode pattern.

Also disclosed herein is an example substrate web for forming aplurality of droplet actuators therefrom. The substrate web includes anon-conductive layer and a conductive layer coupled to thenon-conductive layer. The conductive layer includes a first electrodepattern and a second electrode pattern. The second electrode pattern isspaced apart from the first electrode pattern. The first electrodepattern includes a first marking and the second electrode patternincludes a second marking. The first marking is substantially identicalto the second marking. The substrate web also includes at least one of ahydrophobic layer or a dielectric layer disposed over a substantialentirety of the respective first and second electrode patterns.

In some examples, the first marking and the second marking aresubstantially identical based on at least one of a size or a position ofthe first and second markings on the respective first and secondelectrode patterns.

In some examples, the first electrode pattern includes a plurality oflines and gaps. The lines having a width of about 10 micrometers. Also,in some examples, a thickness of the conductive layer is less than about120 nanometers.

In some examples, the non-conductive layer defines a groove therein. Thegroove is based on the first electrode pattern.

Some examples of the substrate web include an adhesive layer disposedbetween the conductive layer and the non-conductive layer to couple theconductive layer to the non-conductive layer.

In some examples, the first electrode pattern includes lines andspacings, and edges of the lines bordering the spacings aresubstantially smooth. Also, in some examples, the marking is aninterruption to a line defining the electrode pattern.

Also disclosed herein is an example apparatus including a firstsubstrate having a plastic layer and a metal layer. The exampleapparatus also includes an electrode pattern formed in the metal layer.The electrode pattern is insulated by at least one of a hydrophobic or adielectric material. The electrode pattern includes lines having atleast partially curved edges defining spacings between the lines.

In some examples, the example apparatus includes a second substratealigned with the first substrate, wherein the alignment includes a gapbetween the first substrate and the second substrate. In some examples,one or more projections are disposed in the gap. In some examples, theprojections are capillary tubes. Also, in some examples, the secondsubstrate includes at least one of a hydrophobic or a dielectricmaterial.

In some examples, the plastic layer includes a partially curved groovecorresponding to the electrode pattern formed in the metal layer.

Turning now to the figures, FIG. 1 is a diagram of a first examplesystem or assembly 100 for creating a base substrate of a dropletactuator. The first example assembly 100 includes a series or aplurality of rollers, including a first roller 102, a second roller 104,and a third roller 106, which operate in synchronized rotation to drivea base substrate 108 through the first example assembly 100. The firstexample assembly 100 can include rollers in addition to the firstthrough third rollers 102, 104, 106 to move the base substrate 108through the assembly using roll-to-roll techniques. Other examples mayuse conveyors, pulleys and/or any other suitable transport mechanism(s).Prior to cutting or sizing of the base substrate 108 to produceindividual droplet actuators, the base substrate 108 can be considered asubstrate web that may be in a rolled, partially rolled, or unrolledconfiguration as the base substrate 108 moves through the first exampleassembly 100.

In the first example assembly 100, the first roller 102 rotates tounwind the base substrate 108, which, in some examples, is a singlesheet in a rolled configuration. The base substrate 108 includes a firstlayer 110 and a second layer 112. In this example, the first layer 110comprises a non-conductive flexible substrate, such as for example aplastic, and the second layer 112 includes a conductive material. Theconductive material of the second layer 112 can be, for example, a metalsuch as gold, silver, or copper, or a non-metallic conductor, such as aconductive polymer. In other examples different metal(s) orcombination(s) of metal(s) and/or conductive polymer(s) may be used. Insome examples, the base substrate 108 includes an adhesive layer 113disposed between the non-conductive first layer 110 and the conductivesecond layer 112. As an example, the adhesive layer 113 can comprisechrome, with a layer of gold disposed on top of the chrome adhesivelayer 113 to form the conductive second layer 112. Thus, in the basesubstrate 108 of FIG. 1, the non-conductive first layer 110 and theconductive second layer 112 are pre-adhered to form the base substrate108 prior to being unwound by the first roller 102.

In the example base substrate 108 of FIG. 1, the non-conductive firstlayer 110 has a thickness of less than about 500 nm. As will bedescribed below, such a thickness allows for the base substrate 108 tomove through the example first assembly 100 via the plurality ofrollers. Also, in some examples, the thickness of the non-conductivefirst layer 110 is greater than a thickness of the conductive secondlayer 112. As an example, the thickness of the conductive second layer112 can be approximately 30 nm. In other examples, the thickness of theconductive second layer 112 is less than about 500 nm, and in someexamples the thickness of the second layer 112 is less than about 120nm. In some examples, the thickness of the non-conductive first layer110 and/or the conductive second layer 112 is selected based on, forexample, the materials of the first and/or second layers 110, 112 and/oran operational purpose for which the droplet actuator formed from thebase substrate 108 is to be used.

The first roller 102 drives the base substrate 108 to a laser ablationstation 114. The laser ablation station 114 includes a mask 116containing a master pattern 118 that is to be projected onto theconductive second layer 112 of the base substrate 108. The masterpattern 118 associated with the mask 116 may be predefined based oncharacteristics such as resolution (e.g., number of electrodes per anarea of the base substrate 108 to be ablated), electrode size,configuration of lines defining the electrode pattern, inter-digitationof the electrodes, and/or gaps or spacing between the electrodes. Insome examples, the characteristics of the master pattern 118 areselected based on one or more operational uses of the droplet actuatorwith which the base substrate 108 is to be associated (e.g., for usewith biological and/or chemical assays). Also, in some examples, themaster pattern 118 is configurable or reconfigurable to enable the laserablation station 114 to form different patterns on the base substrate108. Additionally or alternatively, in some examples the mask 116 isreplaceable with one or more alternative masks.

The laser ablation station 114 includes a lens 120. As the basesubstrate 108 encounters the laser ablation station 114 as result of therotation of the rollers (e.g., the first roller 102), a portion 122 ofthe base substrate 108 passes under or past the lens 120. The portion122 may be, for example, a rectangular or square section of the basesubstrate 108 having an area less than the area of the base substrate108 and including the conductive second layer 112. The lens 120 imagesor projects at least a portion of the master pattern 118 onto theconductive second layer 112 associated with the portion 122. A laserbeam 124 is directed onto the portion 122 via the mask 116 and the lens120 such that the laser beam 124 selectively penetrates the conductivesecond layer 112 based on the projected master pattern 118. In someexamples, the non-conductive first layer 110 or a portion (e.g., afraction of the thickness of the non-conductive first layer 110) mayalso be penetrated by the laser beam 124 based on the projected masterpattern 118. The solid portions of the mask 116 block the laser beam124, and the open portions of the mask 116 allow the laser beam 124 topass through the mask 116 and into contact with the base substrate 108.The laser beam 124 can be associated with, for example, an excimerlaser.

As a result of exposure to the laser beam 124, the irradiatednon-conductive first layer 110 of the portion 122 absorbs energyassociated with the laser beam 124. The irradiated non-conductive firstlayer 110 undergoes photochemical dissociation, resulting in a selectivebreaking up of the structural bonds of non-conductive first layer 110and ejection of fragments of the non-conductive first layer 110 andportions of the conductive second layer 112 overlaying the irradiatednon-conductive first layer 110 in accordance with the master pattern 118to form an electrode array 126 on the conductive second layer 112. Thus,the ejection of fragments of the non-conductive first layer 110 as aresult of penetration of the laser beam 124 in the non-conductive firstlayer 110 during formation of the electrode array 126 can result instructural changes to the non-conductive first layer 110. Suchstructural changes may alter the appearance of the non-conductive firstlayer 110.

As disclosed above, the laser beam 124 selectively penetrates thenon-conductive first layer 110 and the conductive second layer 112 inaccordance with the master pattern 118 mask 116. Thus, the portions orfragments of the non-conductive first layer 110 that are ejected arebased on the master pattern 118 such that after the fragmentation of thenon-conductive first layer 110, the non-conductive first layer 110includes a feature of the master pattern 118 corresponding to theelectrode array 126. The feature or marking in the non-conductive firstlayer 110 can include, for example, an outline or a substantial outlineof at least a portion of the master pattern 118. In some examples, thenon-conductive first layer 110 includes a disturbance (e.g., a burnmark) formed as a result of the penetration of the laser beam 124 intothe non-conductive first layer 110. The disturbance can include, forexample, a change in the thickness of at least some portion of thenon-conductive first layer 110, an indentation (e.g., a groove) in aportion of the non-conductive first layer 110, or a projection in asurface of the non-conductive first layer 110 (e.g., as a result of thebreaking up and fragmentation of the non-conductive first layer 110).The indentations can include angled or sloped portions forming walls inthe non-conductive first layer 110. Thus, as result of the concurrentexposure of the non-conductive first layer 110 and the conductive secondlayer 112 to the laser beam 124, the non-conductive first layer 110 canundergo one or more structural changes that may be reflected in grooves,projections, markings, discolorations, etc., as will be furtherdisclosed below in connection with FIG. 2E.

In some examples, a depth (e.g., a radiation intensity) to which thelaser beam 124 penetrates the base substrate 108 is predefined based ona depth (e.g., a thickness) of the non-conductive first layer 110 and/orthe conductive second layer 112. In some examples, the laser beam 124penetration depth is adjustable to change the depth at which the laserbeam 124 ablates the conductive second layer 112 as a result of thefragmentation of the underlying non-conductive first layer 110. In someexamples, this adjustment is dynamic as the example system 100 operates.Also, in some examples, the base substrate 108 undergoes cleaning afterexposure to the laser beam 124 to remove particles and/or surfacecontaminants.

As illustrated in FIG. 1, after exposure to the laser ablation station114, the portion 122 of the base substrate 108 includes the electrodearray 126. The electrode array 126 is made up of a plurality ofelectrodes formed into the conductive second layer 112 (FIG. 2A). As aresult of the exposure to the laser beam 124 and fragmentation of thenon-conductive first layer 110, portions of the conductive second layer112 are removed from the base substrate 108. The removed portionsassociated with the electrode array 126 are based on the master pattern118. In some examples, the removed portions match the open portions ofthe mask 116.

For example, FIG. 2A illustrates a top view of the portion 122 of thebase substrate 108 after exposure to the laser ablation station 114 ofthe first example assembly 100 of FIG. 1. As show in FIG. 2A, exposureto the laser beam 124 results in the formation of a laser-ablatedelectrode pattern 200 on the conductive second layer 112. Thelaser-ablated electrode pattern 200 includes lines 202 and spacings 204,which correspond to the master pattern 118 projected onto the portion122 via the lens 120 of FIG. 1.

In the example electrode pattern 200, the lines 202 and the spacings 204define one or more array electrodes 206 that form the electrode array126. The example electrode pattern 200 also includes one or morenon-array electrodes 208. The non-array electrodes 208 that are not apart of the electrode array 126 facilitate external electricalconnections during operation of the droplet actuation. The arrayelectrodes 206 and the non-array electrodes 208 of the electrode pattern200 can vary in size and/or shape. For example, the non-array electrodes208 can be substantially square-shaped whereas the array electrodes 206can be in a configuration other than a square. The shapes and/or sizesof the electrodes 206, 208 of the electrode pattern 200 are defined bythe lines 202 and the spacings 204 in association with the masterpattern 118 projected onto the base substrate 108. As a result offormation via laser ablation, the lines 202 defining the electrodes 206,208 are substantially smooth and/or have substantially reduced roughnesswith respect to the definition of the edges of the electrodes 206, 208as compared to, for example, other methods for forming electrode arrayssuch as photolithography or printed circuit board methods.

In some examples, the lines 202 and/or the spacings 204 formed via laserablation measure (e.g., have a width of) approximately 10 μm; in otherexamples, the lines 202 and/or the spacings 204 are greater or less than10 μm (e.g., about 5 μm). The arrangement and sizes of the lines 202and/or the spacings 204 define a resolution of the electrode array 126.For example, minimal spacings 204 between the lines 202 allows for agreater number of array electrodes 206 in close proximity (e.g.,inter-digitization of the array electrodes 206) within the electrodearray 126 and, as will be disclosed below, reduces an amount ofdielectric and/or hydrophobic material applied between adjacentelectrodes. Thus, the features of the laser ablated electrode pattern200 maximize a surface area of the portion 122 that contributes tooperation of the resulting droplet actuator, thereby reducing an amountof materials necessary to form individual droplet actuators. Further,increased inter-digitation of the array electrodes 206 facilitates anease with which droplets are actuated on the base substrate 108 viamanipulation of electrical potentials. Increased resolution of theelectrode array 126 also improves a precision of droplet sizes that areactuated.

Laser ablation of the portion 122 of the base substrate or web 108 atthe laser ablation station 114 may be achieved via broad field ablationor via rastering. Broad field ablation involves exposure of the laserbeam 124 over substantially the entire portion 122. The master pattern118 is created on the portion 122 by removing material from theconductive second layer 112 with a substantially single instance ofexposure of the non-conductive first layer 110 and the conductive secondlayer 112 to the laser beam 124 (e.g., a single flash of the laser beam124). In broad field laser ablation, the master pattern 118 is thussimultaneously created across the area of the conductive second layer112 associated with the portion 122 to ablate the base substrate 108 athigh speeds. FIG. 2B is a top view of a portion 209 of the electrodepattern 200 of FIG. 2A created via broad field ablation based on themaster pattern 118. As shown in FIG. 2B, the portion 209 includes thelines 202 and the spacings 204 defining the electrode pattern 200. Thelines 202 and/or spacings 204 can have widths of less than 10 μm. Asalso shown in FIG. 2B, edges 211 of the lines 202 are substantiallysmooth and without substantial rough, sharp, pointed, or unevenportions. Such smooth and defined edges 211 result from the irradiationof the base substrate 108 by the laser beam 124 to create the masterpattern 118 with a single exposure of the laser beam 124 on the portion122.

Alternatively, laser ablation can be achieved via rastering or scribing,in which the laser beam 124 iteratively etches the master pattern 118into the portion 122 to form the electrode pattern 200, including theelectrode array 126, in the conductive second layer 112 as the basesubstrate 108 and/or the laser beam 124 moves. In examples whererastering techniques are used, the electrode pattern 200 is determineddigitally without the use of the mask 116. For example, to iterativelyetch the master pattern 118 into the portion 122, the laser beam 124moves along the base substrate 108 to inscribe the master pattern 118into the conductive second layer 112 via a series of individual pulsesin adjacency. The individual pulses result in lines 202 having widthsbetween, for example, 30 and 200 μm. In examples where the rastering isused to form the electrode pattern 200, the edges of the arrayelectrodes 206 may be less smooth due to pulse markings formed by theindividual laser pulses iteratively penetrating the conductive secondlayer 112, as compared to broad field laser ablation.

FIG. 2C is a top view of a portion 214 of the electrode pattern 200 ofFIG. 2A created using laser ablation rastering or scribing techniques.As a result of the indexing of pulses to etch the master pattern 118into the base substrate 108, edges 216 of the lines 202 defining theelectrode pattern 200 differ from the edges 211 of the electrode pattern200 created via broad field laser ablation shown in FIG. 2B. Forexample, the edges 216 of the portion 214 created via rastering includecurved, partially curved, or wave-like features corresponding to theiterative exposure of the portion 214 to individual pulses of the laserbeam 124. Also, because the individual pulses irradiate adjacentportions of the base substrate 108, the curved or wave-like features ofthe edges 216 define a pattern or at least a partial pattern over therespective lines 202 in that in a first curved feature resulting from afirst laser pulse of the laser beam 124 can resemble or partiallyresemble a second curved features resulting from a second laser pulse ofthe laser beam 124. Thus, the edges 216 of the electrode pattern 200created via rastering can be distinguished from electrode patternscreated via techniques such as photolithography, which can result inlines having random, irregularly shaped edges.

FIGS. 2A-C illustrate features of the electrode pattern 200 that arevisible from a top view of the base substrate 108 after exposure to thelaser beam 124 at the laser ablation station 114 of FIG. 1. FIG. 2D is across-sectional view of the portion 122 of the base substrate 108 afterexposure to the laser ablation station 114 of the first example assembly100 of FIG. 1, taken along the 1-1 line of FIG. 2A. As shown in FIG. 2D,the portion 122 includes the non-conductive first layer 110 and theconductive second layer 112 including replications of the electrodearray 126 of the electrode pattern 200 formed across the base substrate108. Although the portion 122 of the base substrate 108 is shown havingthree electrode arrays 126, the portion 122 can include less oradditional electrode arrays 126 of the electrode pattern 200 of FIG. 2A.Also, the portion 122 is part of the base substrate or web 108.

As disclosed above with respect to FIG. 2A, the electrode arrays 126include one or more arrays electrode 206. The laser beam 124 penetratesa thickness t of the conductive second layer 112 as the laser beam 124pulses or etches the lines 202 and corresponding spacings 204 into theconductive second layer 112 to define the array electrodes 206. Thedepth of the penetration of the laser beam 124 into the conductivesecond layer 112 can be based on, for example, the thickness t₁ of theconductive second layer 112 and/or an intensity of the laser beam 124.In some examples, the laser beam 124 penetrates a depth substantiallyequal to the thickness t₁, less than the thickness t₁, or greater thanthe thickness t₁, such that the laser beam 124 penetrates a portion ofthe non-conductive layer 110, as will be disclosed below in connectionwith FIG. 2E. Also, the laser beam 124 defines features of the electrodearray 126 with respect to a resolution or a number of electrodes 206 peran area of the base substrate 108, the size of the array electrodes 206,and the configuration of lines 202 and the spacings 204 therebetween,which define a degree of inter-digitation of the array electrodes 206.

Although laser ablation results in a well-defined electrode pattern 200including the electrode array 126 having increased resolution, in someexamples, defects or imperfections in the mask 116 or the lens 120 canresult corresponding defects in the based substrate 108. Such defectscan include debris on the mask 116 or the lens 120, openings in the mask116 that allow the laser beam 124 to irradiate the base substrate 108where such exposure was not intended (e.g., an additional opening in themask 116 or a wider than intended opening), and/or imperfections in themask 116 that prevent the laser beam 124 from penetrating the basesubstrate 108 where the penetration was intended (e.g., incompleteopenings in the mask 116). Debris (e.g., hair, dust, etc.) orimperfections in the mask 116 can result in interruptions orinconsistencies in the resulting electrode pattern 200, such as gaps oralterations to the shapes of the lines 202 and/or the spacings 204defining the electrode pattern 200). Another example of a defectincludes inconsistencies in the spacings 204 in the master pattern 118due to a defect in the master pattern 118.

FIG. 2D illustrates the conductive second layer 112 of the basesubstrate 108 including defects or markings 212. In the example portion122, the defects 212 are included in each of the iterations of theelectrode array 126 of the electrode pattern 200 across the basesubstrate 108. However, the defects 212 can be located elsewhere in theelectrode pattern 200, such as in connection with the non-arrayelectrodes 208. In examples where the electrode pattern 200 is formedusing broad field laser ablation, the defects 212 are systematic, orsubstantially identical in each of the electrode arrays 126 of theportion 122. In particular, the systematic occurrences of the defects212 results from the exposure of the laser beam 124 over substantiallythe entire portion 122 to concurrently form multiple electrode patterns200. Thus, the defects 212 are substantially uniformly replicated ineach of the electrode patterns 200 irradiated into the conductive secondlayer 112 as the base substrate 108 is exposed to the laser beam 124 atthe laser ablation station 114. For example, the defects 212 can bedisposed at substantially the same position relative to the respectiveelectrode patterns 200. Also, the defects 212 can be the substantiallythe same size within the respective electrode patterns 200. Therefore,the resulting substrate web, including the base substrate 108 and theelectrode patterns 200, includes substantially identical, systematicallyreproduced defects 212 in each of the electrode patterns 200.

In some examples, markings such as the defects 212, could be purposeful.For example, such markings may be included as a signature that appearsacross all electrodes patterns 200 to identify a particularmanufacturer, manufacturing run, product, or manufacturing location.

FIG. 2E is a cross-sectional view of the portion 122 including theelectrode pattern 200 taken along the 2-2 line of FIG. 2A. As anexample, FIG. 2E illustrate a section of the electrode pattern 200 otherthan the electrode array 126. For example, FIG. 2E illustrates the lines202 and the spacings 204 defining one or more of the non-arrayelectrodes 208.

As disclosed above with respect to the exposure of the base substrate108 to the laser beam 124 in connections with FIGS. 1 and 2D, in someexamples, the laser beam 124 selectively penetrates through theconductive second layer 112 and the non-conductive first layer 110. Insuch examples, the laser beam 124 penetrates through the thickness t₁ ofthe conductive second layer 112 and a thickness t₂ of the non-conductivefirst layer 110, which may be less or substantially less than a totalthickness t₃ of the non-conductive first layer 110. The non-conductivefirst layer 110 absorbs some of the energy of the laser beam 124. As aresult of the irradiation of the non-conductive first layer 110, aportion of the non-conductive first layer 110 having the thickness t₂ isejected from the non-conductive first layer 110, which results instructural changes to the non-conductive first layer 110. The ejectionof the portion of the non-conductive first layer 110 can result inejection of a portion of the conductive second layer 112 to define theelectrode pattern 200. As illustrated in FIG. 2E, the non-conductivefirst layer 110 includes one or more disturbances 210 due to thepenetration of the laser beam 124. The portions or disturbances 210includes indentations, spacings, openings, or grooves in thenon-conductive first layer 110 resulting from the ejection of one ormore portions of the irradiated non-conductive first layer 110. Therespective thicknesses of the disturbances 210 depend on the thicknessof the non-conductive first layer 110 and a depth of the penetration ofthe laser beam 124. Also, although the disturbances 210 are illustratedin FIG. 2E as rectangular in shape, the disturbances 210 can besubstantially any shape including irregularly shaped, curved, or angledgrooves or indentations corresponding to the shape of the fragmentsejected from the non-conductive first layer 110.

Although laser ablation of the base substrate 108 at the laser ablationstation 114 has been described with respect to the portion 122, it is tobe understood that, as part of the continuous movement of the basesubstrate 108 through the first example assembly 100 via the firstthrough third rollers 102, 104, 106, the laser beam 124 penetrates morethan one portion of the base substrate 108 during operation of the firstexample assembly 100. In the first example assembly 100, as the basesubstrate 108 passes under and/or by the lens 120, successive portions nof the conductive second layer 112 are exposed to the laser beam 124 forrepeatedly creating the master pattern 118 on each of the successiveportions n. The size of the portions and the spacing between theportions as the base substrate 108 passes through the laser ablationstation 114 may be predetermined based on, for example, the size andconfiguration of the master pattern 118, the dimensions of the basesubstrate 108, the thickness of the conductive second layer 112, and/orthe dimensions of the droplet actuator with which the base substrate 108will be associated.

Returning to FIG. 1, after the portion 122 undergoes laser ablation atthe laser ablation station 114 to form the electrode array 126 (e.g., aspart of the electrode pattern 200 of FIG. 2A), the portion 122 is moved,via rotation of the first through third rollers 102, 104, 106, to aprinter 128. In the first example assembly 100, the printer 128 includesan apparatus or an instrument capable of applying at least one layer ofmaterial 130 having a hydrophobic and/or a dielectric property to theelectrode array 126. In the first example assembly 100, the printer 128can deposit the hydrophobic and/or dielectric material 130 viadeposition techniques including, but not limited to, web-based coating(e.g., via rollers associated with the printer 128), slot-die coating,spin coating, chemical vapor deposition, physical vapor deposition,and/or atomic layer deposition. The printer 128 can also apply othermaterials in addition to the hydrophobic and/or dielectric material 130(e.g., anti-fouling coatings, anti-coagulants). Also, the printer 128can apply one or more layers of the material(s) with differentthicknesses and/or covering different portions of the base substrate108.

As described above, in the first example assembly 100, at least one ofthe first through third rollers 102, 104, 106 advance the base substrateor web 108 to the printer 128 for application of the hydrophobic and/ordielectric material 130 to the electrode array 126. In some examples,the printer 128 includes a plurality of registration rollers 131 tofacilitate accuracy in feeding and registration of the base substrate108 as part of operation of the printer 128 in applying the hydrophobicand/or dielectric material 130, for example, via roller coating methods.

In the first example assembly 100, the hydrophobic and/or dielectricmaterial 130 is applied to the electrode array 126 to completely orsubstantially completely insulate the electrode array 126. For example,referring again to FIG. 2A, the printer 128 selectively applies thehydrophobic and/or dielectric material 130 to the electrodes 206 of theelectrode array 126, however, the printer 128 does not apply thehydrophobic and/or dielectric material 130 to the other electrodes 208of the electrode pattern 200. The selective application of thehydrophobic and/or the dielectric material 130 to the electrode pattern200 provides for electrodes that are capable of making electricalcontact with other electrodes (e.g., the non-array electrodes 208 thatare not covered with the hydrophobic and/or dielectric material 130) aswell as electrodes that are covered or coated as part of the electrodearray 126 (e.g., the array electrodes 206). As a result of thehydrophobic and/or the dielectric material 130, a droplet placedproximate to the electrode array 126 is in a beaded configurationforming a contact angle with respect to the portion 122. In operation,the electrodes 206 of the coated electrode array 126 control the contactangle (e.g., a degree of the contact angle) via electric forces.

In some examples, the hydrophobic and/or dielectric material 130 is apolytetrafluoroethylene material (e.g., Teflon®) or a fluorosurfactant(e.g., FluoroPel™) applied to the conductive second layer 112 tosubstantially cover the electrode array 126. In other examples, thehydrophobic and/or dielectric material 130 is a dielectric such as aporcelain (e.g., a ceramic) or a plastic. In some examples, a dielectricis applied in combination with the hydrophobic material, such that theelectrode array 126 is coated with a first layer of the dielectric and asecond layer of, for example, Teflon® disposed on to the dielectriclayer. In such examples, the first layer of dielectric may have agreater thickness than the second layer of the treated layer. Also, insome examples, an anti-fouling coating is applied to the electrode array126 (e.g., as an additional layer or in connection with the hydrophobicand/or dielectric material 130) to reduce surface fouling that canresult from accumulation of proteins other biological species duringclinical use of the resulting droplet actuator and that may result incontamination of the microfluidic device. Other materials can be appliedbased on operational use of the droplet actuator. For example, ananti-coagulant material can be applied to prevent clotting of abiological specimen before an assay is completed.

In some examples, the hydrophobic and/or dielectric material 130 isdeposited via the printer 128 in substantially liquid form. To create astructural, or treated layer 132 on the base substrate 108 to support adroplet, the portion 122 is moved via the rollers (e.g., the firstthrough third rollers 102, 104, 106) through a curing station 134. Atthe curing station 134, the hydrophobic and/or dielectric material istreated and/or modified to form the first treated layer 132. Treatingand/or modifying the hydrophobic and/or dielectric material can includecuring the material. For example, at the curing station 134, heat isapplied to facilitate the hardening of the hydrophobic and/or dielectricmaterial 130. In some examples, the portion 122 is exposed to anultraviolet light to cure the hydrophobic and/or dielectric material 130and form the treated layer 132 to insulate the electrode array 126. Inother examples, the curing and/or modification of the hydrophobic and/ordielectric material is accomplished without heat and/or a photon source.In some examples, the treated layer 132 supports a droplet as anelectric field is applied (e.g., in connection with electrode array 126)to manipulate the droplet. For example, during an electrowettingprocess, a contact angle of the droplet with respect to the treatedlayer 132 changes as a result of an applied voltage, which affects thesurface tension of the droplet on the treated surface 132.

After passing through the curing station 134, the portion 122 isprepared to serve as a bottom substrate of a droplet actuator and/or asa digital microfluidic chip. Because the base substrate 108 includes thenon-conductive first layer 110 bonded with the conductive second layer112, as disclosed above, additional adhesion of, for example, theelectrode array 126 to the non-conductive first layer 110 is notrequired. Such a pre-adhered configuration increases the efficiency ofthe preparation of the base substrate 108 for the droplet actuator byreducing processing steps. Also, as described above, when the portion122 is at any one of the laser ablation station 114, the printer 128, orthe curing station 134, other portions n of the base substrate 108 areconcurrently moving through the others of the respective stations 114,128, 134 of the first example assembly 100. For example, when theportion 122 is at the curing station 134, the first through thirdrollers 102, 104, 106 are continuously, periodically, or aperidiocallyadvancing one or more other portions n of the base substrate 108through, for example, the laser ablation station 114 and/or the printer128. In such a manner, preparation of the base substrate 108 for thedroplet actuator is achieved via a substantially continuous, high-speed,automated process.

Although the base substrate 108 may be considered as includingsuccessive portions, during some example operations of the first exampleassembly 100, the base substrate 108 remains as a single sheet or web asthe successive portions undergo processing to create the electrodearrays 126 (e.g., via the electrode pattern 200 of FIG. 2A) and receivethe coating of hydrophobic and/or dielectric material 130. Thus, tocreate one or more droplet actuators using the processed base substrate108, the base substrate or web 108, in some examples, is cut (e.g.,diced) to form individual units comprising the electrode arrays 126, aswill be further disclosed below (e.g., FIGS. 4, 6). In some examples,prior to dicing, the base substrate 108, including the portion 122, isrewound in a rolled configuration similar to the initial rolledconfiguration of the base substrate 108 prior to being unwound by thefirst roller 102. Such rewinding may be accomplished via one or morerollers as part of the roll-to-roll processing. In such examples, thebase substrate 108 may be diced or otherwise separated at a later time.In other examples, the rollers (e.g., the second and third rollers 104,106), advance the base substrate 108 for merging with a top substrate,as will be further disclosed below (e.g., FIGS. 4, 6).

As described above, an example droplet actuator includes a basesubstrate, such as the base substrate 108 including the electrode array126 (FIGS. 1 and 2) and a top substrate. The top substrate may includefor example, an electrode pattern and associated electrode array createdvia laser ablation in substantially the same manner as the electrodepattern 200 and electrode array 126 of FIGS. 1 and 2, a single electrode(e.g., a layer of a conductive metal), or a non-conductive substrate(e.g., a dielectric). Alternatively, in some examples, the dropletactuator does not include a top substrate. In preparing the topsubstrate and/or a configuration of the top substrate, consideration isgiven to, for example, intended applications of the droplet actuator.

FIG. 3 illustrates a second example assembly 300 for creating an exampletop substrate of a droplet actuator having a single electrode. Thesecond example assembly 300 includes a series or a plurality of rollers,including a first roller 302, a second roller 304, and a third roller306, which operate in synchronized rotation to drive a top substrate 308through the second example assembly 300. The second example assembly 300can include rollers in addition to the first through third rollers 302,304, 306 to move the top substrate 308 through the assembly 300. Priorto cutting or sizing of the top substrate 308, the top substrate 308 canbe considered a substrate web that may be in a rolled, partially rolled,or unrolled configuration as the top substrate 308 moves through thesecond example assembly 300.

In the second example assembly 300, the first roller 302 rotates tounwind the top substrate 308, which, in some examples, is a sheet in arolled configuration. The example top substrate 308 of FIG. 3 includes afirst layer 310 and a second layer 312. As with the example basesubstrate 108, in this example, the example first layer 310 of the topsubstrate 308 comprises a non-conductive material such as, for example,a plastic, and the example second layer 312 includes a conductivematerial, such as a metal including, for example, one or more of gold,chrome, silver, or copper and/or any other suitable metal(s), conductivepolymer(s), or combination(s) of metal(s) and/or conductive polymer(s).In some examples, the conductive second layer 312 is adhered to thenon-conductive first layer 310 via an adhesive layer (e.g., chrome).

In the second example assembly 300, the first through third rollers 302,304, 306 rotate to advance the top substrate 312 to a printer 314. Theprinter 314 coats the conductive second layer 312 with a hydrophobicand/or dielectric material 316 (e.g., Teflon® or a dielectric such as aceramic). The printer 314 is substantially similar to the printer 128 ofthe first example assembly 100 of FIG. 1. For example, the printer 314can apply the hydrophobic and/or dielectric material 316 to the topsubstrate 308 via web-based coating, slot-die coating, spin coating,chemical vapor deposition, physical vapor deposition, atomic layerdeposition, and/or other deposition techniques. The printer 314 caninclude registration rollers 317 to facilitate alignment of the topsubstrate 308 with respect to the printer 314 during application of thehydrophobic and/or dielectric material 316 and/or other coatingmaterials.

After receiving the coating of the hydrophobic and/or dielectricmaterial 316, the second roller 104 and the third roller 106 advance theportion 318 to a curing station 320. As disclosed in connection with thecuring station 134 of FIG. 1, the curing station 320 of the secondexample assembly 300 facilitates the modification (e.g., curing) of thehydrophobic material via heat to form a treated layer 322. The treatedlayer 322 insulates the conductive second layer 312, which serves as thesingle electrode of the top substrate 308, by completely orsubstantially completely covering the conductive second layer 312. Thus,in coating the second layer 312 of the portion 318, electrical potentialconducting portion of the top substrate 308 is insulated from a dropletthat may be applied to a droplet actuator that includes the portion 318.

After passing through the curing station 320, the portion 318 isprepared to serve as a top substrate of a droplet actuator. Because thetop substrate 308 includes the non-conductive first layer 310pre-adhered to the conductive second layer 312 prior to processing ofthe top substrate via the second example assembly 300, additionaladhesion of, for example, an electrode to the non-conductive first layer310 is not required, thereby increasing the efficiency of thepreparation of the top substrate 308 for the droplet actuator.

Also, and as disclosed in connection with the first example assembly 100of FIG. 1, in the second example assembly 300, the first through thirdrollers 302, 304, 306 rotate to advance the top substrate 308 such thatportions of the top substrate pass through one of the printer 314 or thecuring station 320 in substantially continuous, periodic and/oraperiodic succession as part of the roll-to-roll operation of the secondexample assembly 300. Thus, although the second example assembly 300 isdescribed in association with the portion 318, it is to be understoodthat successive portions of the top substrate 308 are prepared insubstantially the manner as the portion 318 as a result of rotation ofthe first through third rollers 302, 304, 306. In such as manner, thetop substrate 308 is provided with a treated layer 322 along the lengthof the top substrate 308.

In the example top substrate 308, the conductive second layer 312 servesan electrode. However, in some examples, the conductive second layer 312undergoes laser ablation to form one or more electrode arrays. In suchexamples, the second example assembly 300 includes a laser ablationstation substantially similar to the laser ablation station 114 of thefirst example assembly 100 of FIG. 1. Thus, prior to receiving thehydrophobic material 316, the top substrate 308 is exposed to a laserbeam, which creates an electrode pattern in the irradiated conductivesecond layer 312. The electrode pattern formed on the top substrate 308can be the same or different from the electrode pattern formed on thebase substrate 108 of FIG. 1. In examples where the top substrate 308 isablated via a laser, the second example assembly 300 is substantiallysimilar to the first example assembly 100. Also, in some examples, theelectrode array is not formed on/in the base substrate 108 but onlyon/in the top substrate 308.

During operation of the second example assembly 300, the top substrateremains single sheet as successive portions of the top substrate 308 arecoated with the hydrophobic material 316. As part of the fabrication ofone or more droplet actuators, the top substrate 308 is aligned with thebase substrate (e.g., the base substrate 108 of FIG. 1). In someexamples, after passing through the curing station 320, the topsubstrate is rewound into a rolled configuration via one or morerollers. In such examples, the finished roll may be diced or otherwisecut and/or separated into individual units that are aligned at a spaceapart distance and bonded with individual diced units of the basesubstrate 108 of FIG. 1 to create a droplet actuator.

In other examples, after passing through the curing station 320, therollers (e.g., the first through third rollers 302, 304, 306) continueto advance the top substrate 308 to merge the top substrate 308 with thebase substrate 108 of FIG. 1 via automated roll-to-roll processing, aswill be discussed below in connection with FIG. 4. In such examples, toprepare the top substrate 308 for alignment with the base substrate 108,the rollers of the second example assembly 300 (e.g., the first throughthird rollers 302, 304, 306) rotate so as to reverse the orientation ofthe top substrate 308 relative to the base substrate 108 of FIG. 1 suchthat the treated layer 132 of the base substrate 108 faces the treatedlayer 322 of the top substrate 308 when the base substrate 108 and thetop substrate 308 are aligned in parallel configuration (see, e.g., FIG.4).

FIG. 4 is a diagram of a third example assembly 400 for processing thesubstrate webs. The example assembly 400 operates to merge a basesubstrate with a top substrate to fabricate a droplet actuator viaroll-to-roll processing. The third example assembly 400 can beimplemented in connection with the first example assembly 100 of FIG. 1and the second example assembly 300 of FIG. 3 to fabricate a dropletactuator from the base substrate 108 of FIG. 1 and the top substrate 308of FIG. 3. For example, as shown in FIG. 4, after passing through thecuring station 320 associated with the second example assembly 300, thetop substrate 308 is advanced by a first roller 402 of the third exampleassembly 400. Similarly, after passing through the curing station 134associated with the first example assembly 100, the base substrate 108is advanced by a second roller 402 of the third example assembly 400 tofacilitate alignment of the substrates 108, 308.

The third example assembly 400 includes a third roller 406 and a fourthroller 408 that form a pair of merging rollers to which the basesubstrate 108 and the top substrate 308 are fed via the respective firstroller 402 and the second roller 404 of the third example assembly 400.As each of the merging rollers 406, 408 rotates, the base substrate 108and the top substrate 308 are aligned in a parallel configuration at apredetermined spaced apart distance, or gap.

For example, FIG. 4 illustrates a merged portion 410 including the basesubstrate 108 and the top substrate 308 in parallel alignment andincluding a gap 412 separating the treated layer 132 of the basesubstrate 108 and the treated layer 322 of the top substrate 108. Thegap 412 is a predetermined spaced apart distance between the treatedlayers 132, 322. The gap 412 can be created using one more gap formationtechniques. Such techniques can include, for example, inserting one ormore capillary tubes and/or microbeads between the base and topsubstrates 108, 308 to serve as spacers to separate the respectivetreated layers 132, 322. Additionally or alternatively, other examplesfor forming and/or maintaining the gap include embossing or moldingpillars into, for example, the non-conductive first layer 110 of thebase substrate 108 to provide a frame to separate the base substrate 108and the top substrate 308. Further still, other additional oralternative examples for forming and/or maintaining the gap includelaminating one or more of the treated layers 132, 322 of the respectivebase substrate 108 and the top substrate 308 to create a film toseparate the substrates or spraying a filler fluid (e.g., a fluidimmiscible with the droplet fluid) on at least a portion of thesubstrates 108, 308. In some examples, the gap formation techniques maybe implemented via roll-to-roll processing. For example, as one or morethe base substrate 108 or the top substrate 308 passes proximate to oneor more rollers of the first through third example assemblies 100, 300,400, one or more of the rollers may provide for embossing and/orlamination of the base substrate 108 and/or the top substrate 308.

Similarly, in examples where the base substrate 108 and the topsubstrate 308 are rewound as individual rolls (e.g., as part of thefirst example assembly 100 of FIG. 1 and the second example assembly 300of FIG. 3), diced separately, and then aligned, the base substrate 108and the top substrate 308 are also arranged so that a gap exists betweentreated layers 132, 322 of the respective base substrate 108 and the topsubstrate 308.

As show in FIG. 4, the example third assembly 400 includes a bondingstation 414. The bonding station 414 joins, or bonds, the base substrate108 and the top substrate 308 as part of fabricating the dropletactuator. For example, at the bonding station 414, one or more adhesivesmay be selectively applied to a predefined portion of the base substrate108 and/or the top substrate 308 (e.g., a portion of the base substrate108 and/or the top substrate 308 defining a perimeter of the resultingdroplet actuator) to create a bond between the base substrate 108 andthe top substrate 308 while preserving the gap 412. In some examples,bonding the substrates 108, 308 at the bonding station 414 includingforming the gap 412 (e.g., in advance of applying the adhesive).

Examples of adhesive(s) that may be used at the bonding station 414include epoxies, foils, tapes, and/or ultraviolet curable adhesives. Insome examples, layers of polymers such as SU-8 and/orpolydimethylsiloxane (PDMS) are applied to the base substrate 108 and/orthe top substrate 308 to bond the substrates. Also, in some examples,the bonding station 414 provides for curing of the adhesive(s) via, forexample, ultraviolet light. The bonding station 414 may apply one moremethods involving, for example, heat (e.g. thermal bonding), pressure,curing, etc. to bond the base substrate 108 and the top substrate 308.

In the example third assembly 400, the merged portion 410 can beselectively cut, diced or otherwise separated to form one or moredroplet actuators, as substantially represented in FIG. 4 by the mergedportion 410. The example third assembly 400 includes a dicing station416. The dicing station 416 can be, for example, a cutting device, asplitter, or more generally, an instrument to divide the continuousmerged portion 410 into discrete units corresponding to individualdroplet actuators. The merged portion 410 may be cut into individualdroplet actuators based on, for example, the electrode pattern 200 ofFIG. 2A such that each droplet actuator includes a footprint of theelectrode array 126 and the other electrodes that are formed via theelectrode pattern 200 (e.g., the non-array electrodes 208). Duringoperation of the resulting droplet actuator, the gap 412 can receive adroplet that can be manipulated using electrical potentials via theinsulated electrodes 206 of the electrode array 126 of the basesubstrate 108 (e.g., the conductive second layer 112) and/or theinsulated electrode of the top substrate 312 (e.g., the conductivesecond layer 312). The insulated nature of the conductive surfaces ofthe base substrate 108 and the top substrate 108 prevents unintendedchemical reactions or changes to the droplet fluid due to exposure tothe electrodes, thereby protecting the integrity of the dropletmanipulation and analysis.

FIG. 5 is a block diagram of an example processing system 500 for usewith a droplet actuator fabrication assembly such as, for example, thefirst, second, and/or third example assemblies 100, 300, 400 of FIGS. 1,3 and 4 for processing one or more substrate webs. The exampleprocessing system 500 includes a controller 502, which controlsoperation the first, second, and/or third example assembles 100, 300,400 via selected driver components.

For example, the example processing system 500 includes a roller driver504, which controls one or more of the rollers of the first, second,and/or third example assembles 100, 300, 400. In some examples, theexample processing system 500 includes one or more roller drivers 504.In the example shown, the roller driver(s) 504 are communicativelycoupled to rollers 506 a-n. The rollers 506 a-n may correspond, forexample, to the first through third rollers 102, 104, 106 of the firstexample assembly 100; the first through third rollers 302, 304, 306 ofthe second example assembly 300; and/or the first through fourth rollers402, 404, 406, 408 of the third example assembly 400. The rollerdriver(s) 504 control rotation of the rollers 506 a-n using, forexample, a motor, to regulate one or more operational characteristics ofthe rollers. Such operational characteristics may include speed ofrotation, duration of rotation, direction of rotation, acceleration,etc. of the rollers 506 a-n. One or more of the operationalcharacteristics controlled by the roller driver(s) 504 at leastpartially determine a position of a portion of the one or moresubstrates fed through the first, second, and third example assemblies100, 300, 400 (e.g., the portion 122 of the base substrate 108, theportion 318 of the top substrate 308, and/or the merged portion 410) atany time during the operation of the rollers 506 a-n. Further, one ormore of the operational characteristics controlled by the rollerdriver(s) 504, such as speed of rotation, at least partially determine aduration for which a portion of the substrates is exposed to one or morestations of the first, second, and third example assemblies 100, 300,400 (e.g., the laser ablation station 114 of the first example assembly100). Thus, the roller driver(s) 504 control rate at which the one ormore substrates are processed. Also, an example processor 508 operatesthe roller driver(s) 604 and, thus, the first, second, and third exampleassemblies 100, 300, 400 in accordance with a droplet actuatorfabrication protocol.

The example processing system 500 also includes a laser driver 510. Insome examples, the example processing system 500 includes one or morelaser drivers 510. In the example shown, the one or more laser driver(s)510 are communicatively coupled to one or more lasers 512 to control thelaser(s) 512. The laser(s) 512 may correspond to, for example, the laserbeam 124 of the laser ablation station 114 of the first example assembly100. In some examples, the second example assembly 400 includes a laserablation station having a laser beam. In such examples, the laserdriver(s) 510 also control the laser associated with the second exampleassembly 400. The laser driver(s) 510 control, for example, theintensity of the laser(s) 512, a size of surface area of irradiationwith respect to the substrate(s), the depth to which the laser(s) 512penetrate a substrate (e.g., the conductive second layer 112 and thenon-conductive first layer 110 of the base substrate 108), and/or aduration for which the laser(s) 512 do or do not penetrate thesubstrate. The laser driver(s) 510 also control a manner in which thelaser(s) 512 are exposed on the substrate(s), including whether thelaser(s) 512 iteratively irradiate the substrate(s) as part of laserablation rastering techniques or whether the laser(s) 512 are exposedover an predetermined surface area of the substrate(s) for inscribing anelectrode pattern in the substrate(s) via a single exposure of the laservia broad field laser ablation. In examples where the laser(s) 512iteratively etch the pattern into the substrate(s), the laser driver(s)510 control the movement (e.g., direction and speed) of the laser(s) 512across the substrate(s). Also, the example processor 508 operates thelaser driver(s) 510 and, thus, the laser(s) 512 in accordance with alaser ablation protocol.

The example processing system 500 also includes a printer driver 514which controls one or more of the printers of the first and/or secondexample assemblies 100, 300. In some examples, the example processingsystem 500 includes one or more printer drivers 514. In the exampleshown, the printer driver(s) 514 are communicatively coupled to a firstprinter 516 and a second printer 518. The first printer 516 maycorrespond, for example, to the printer 128 of the first exampleassembly 100. The second printer 518 may correspond, for example, to theprinter 314 of the second example assembly 300. The printer driver(s)514 control, for example, the thickness, width, and/or pattern of thehydrophobic and/or dielectric material applied to the substrates by thefirst printer 516 and the second printer 518. In examples where thehydrophobic and/or dielectric material is applied via web-basedprinting, the printer driver(s) 514 can control a pressure with whichrollers associated with the first printer 516 and/or the second printer518 contact the substrates and thus, affect the quality of thehydrophobic and/or dielectric layer of material applied to the electrodearray. In some examples, the first printer 516 and the second printer518 operate in connection with the rollers 506 a-n. In such examples,the printer driver(s) 514 work in association with the roller driver(s)504 to define, for example, a rate at which the hydrophobic and/ordielectric material is deposited on the substrates. Also, the exampleprocessor 508 operates the printer driver(s) 514 and, thus, the firstprinter 516 and the second printer 518 in accordance with a hydrophobicand/or dielectric material application protocol.

The example processing system 500 also includes a curing station driver520 that controls one or more of the curing stations of the first and/orsecond example assembles 100, 300. In some examples, the exampleprocessing system 500 includes one or more curing station drivers 520.In the example shown, the curing station driver(s) 520 arecommunicatively coupled to a first curing station 522 and a secondcuring station 524. The first curing station 522 may correspond, forexample, to the first curing station 134 of the first example assembly100. The second curing station 524 may correspond, for example, to thesecond curing station 320 of the second example assembly 300. The curingstation driver(s) 520 control, for example, the intensity of heat and/orultraviolet light applied to the substrates, the size of an area of thesubstrates exposed to the heat and/or ultraviolet light, a duration ofexposure of the heat and/or ultraviolet light, etc. Also, the exampleprocessor 508 operates the curing station driver(s) 520 and, thus, thefirst curing station 522 and the second curing station 524 in accordancewith a hydrophobic and/or dielectric material curing protocol.

The example processing system 500 also includes a bonding station driver526 that controls the bonding station of the third example assembly 400.In some examples, the example processing system 500 includes one or morebonding station drivers 526. In the example shown, the bonding stationdriver(s) 526 are communicatively coupled to a bonding station 528. Thebonding station 528 may correspond, for example, to the bonding station414 of the third example assembly 400. The bonding station driver(s) 526control, for example, a thickness with which the adhesive is applied, aconfiguration or layout in which the adhesive is applied, a durationand/or intensity of heat applied to facilitate curing or thermalbonding, a pressure applied to bond the substrates, etc. In someexamples, the bonding station driver(s) also control formation of a gapbetween the substrates (e.g., via lamination). Also, the exampleprocessor 508 operates the bonding station driver(s) 526 and, thus, thefirst bonding station 528 in accordance with a substrate bondingprotocol.

The example processing system 500 also includes a dicing station driver530 that controls the dicing station of the third example assembly 400.In some examples, the example processing system 500 includes one or moredicing station drivers 526. In the example shown, the dicing stationdriver(s) 530 are communicatively coupled to a dicing station 532. Thedicing station 532 may correspond, for example, to the dicing station416 of the third example assembly 400. The dicing station driver(s) 530control, for example, the cutting or splitting of the substrate webs(e.g., the bonded substrates or, in some examples, the substrates asindividual layers), a size of the discrete units into which thesubstrates are cut, a spacing between discrete units formed from thecontinuous substrates, an operational speed of a cutting instrument,retraction of the cutting instrument, etc. Also, the example processor508 operates the dicing station driver(s) 530 and, thus, the dicingstation 532 in accordance with a substrate web dicing protocol.

The example processing system 500 also includes a database 534 that maystore information related to the operation of the example system 500.The information may include, for example, information about the lengthand dimensions of the substrates to be fed through the first, second,and/or third example assemblies 100, 300, 400; the materials comprisingthe substrates (e.g., type of metal of the conductive second layer 112of the base substrate 108), rotational characteristics of the rollers,such as a speed and/or diameter; the electrode pattern(s) to be ablatedon the substrate(s) via the laser(s); properties of the hydrophobic,dielectric, adhesive, and/or other material(s) to be applied to thesubstrates, etc.

The example processing system 500 also includes a user interface suchas, for example, a graphical user interface (GUI) 536. An operator ortechnician interacts with the processing system 500, and thus, thefirst, second, and/or third example assemblies 100, 300, 400 via theinterface 536 to provide, for example, commands related to operation ofthe rollers 506 a-n such as speed, duration of rotation, etc. of therollers; the pattern(s) to be ablated on the substrates via the laser(s)512; the intensity of the laser(s) 512; the type of hydrophobic and/ordielectric material(s) to be applied to the substrates by the printers;the intensity of the curing stations 522, 524; the size of the gap inaligning the base substrate and top substrate via the rollers 506 a-n,the adhesives applied to bond the substrates at the bonding station 528;the size of the discrete units into which the substrates are cut via thedicing station 532; etc. The interface 536 may also be used by theoperator to obtain information related to the status of any substrateprocessing completed and/or in progress, check parameters such as speedand alignment, and/or to perform calibrations.

In the example shown, the processing system components 502, 504, 508,510, 514, 520, 526, 530, 534 are communicatively coupled to othercomponents of the example processing system 500 via communication links538. The communication links 538 may be any type of wired connection(e.g., a databus, a USB connection, etc.) and/or any type of wirelesscommunication (e.g., radio frequency, infrared, etc.) using any past,present or future communication protocol (e.g., Bluetooth, USB 2.0, USB3.0, etc.). Also, the components of the example system 500 may beintegrated in one device or distributed over two or more devices.

While an example manner of implementing the first, second, and/or thirdexample assemblies 100, 300, 400 of FIGS. 1, 3, and 4 is illustrated inFIG. 5, one or more of the elements, processes and/or devicesillustrated in FIG. 5 may be combined, divided, re-arranged, omitted,eliminated and/or implemented in any other way. Further, the examplecontroller 502, the example roller driver(s) 504, the example processor508, the example laser driver(s) 510, the example printer driver(s) 514,the example curing station driver(s) 520, the example bonding stationdriver(s) 526, the example dicing station driver(s) 530, the exampledatabase 534 and/or, more generally, the example processing system 500of FIG. 5 may be implemented by hardware, software, firmware and/or anycombination of hardware, software and/or firmware. Thus, for example,any of the example controller 502, the example roller driver(s) 504, theexample processor 508, the example laser driver(s) 510, the exampleprinter driver(s) 514, the example curing station driver(s) 520, theexample bonding station driver(s) 526, the example dicing stationdriver(s) 530, the example database 534 and/or, more generally, theexample processing system 500 of FIG. 5 could be implemented by one ormore analog or digital circuit(s), logic circuits, programmableprocessor(s), application specific integrated circuit(s) (ASIC(s)),programmable logic device(s) (PLD(s)) and/or field programmable logicdevice(s) (FPLD(s)). When reading any of the apparatus or system claimsof this patent to cover a purely software and/or firmwareimplementation, at least one of the example controller 502, the exampleroller driver(s) 504, the example processor 508, the example laserdriver(s) 510, the example printer driver(s) 514, the example curingstation driver(s) 520, the example bonding station driver(s) 526, theexample dicing station driver(s) 530, and/or the example database 534is/are hereby expressly defined to include a tangible computer readablestorage device or storage disk such as a memory, a digital versatiledisk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing thesoftware and/or firmware. Further still, the example processing system500 of FIG. 5 may include one or more elements, processes and/or devicesin addition to, or instead of, those illustrated in FIG. 5, and/or mayinclude more than one of any or all of the illustrated elements,processes and devices.

A flowchart representative of example machine readable instructions forimplementing the first, second, and third example assemblies 100, 300,400 and/or the example processing system 500 of FIGS. 1, and 3-5 isshown in FIG. 6. In this example, the machine readable instructionscomprise a program for execution by a processor such as the processor712 shown in the example processor platform 700 discussed below inconnection with FIG. 7. The program may be embodied in software storedon a tangible computer readable storage medium such as a CD-ROM, afloppy disk, a hard drive, a digital versatile disk (DVD), a Blu-raydisk, or a memory associated with the processor 712, but the entireprogram and/or parts thereof could alternatively be executed by a deviceother than the processor 712 and/or embodied in firmware or dedicatedhardware. Further, although the example program is described withreference to the flowchart illustrated in FIG. 6, many other methods ofimplementing the example first, second, and third example assemblies100, 300, 400 and/or the example processing system 500 may alternativelybe used. For example, the order of execution of the blocks may bechanged, and/or some of the blocks described may be changed, eliminated,or combined.

As mentioned above, the example process of FIG. 6 may be implementedusing coded instructions (e.g., computer and/or machine readableinstructions) stored on a tangible computer readable storage medium suchas a hard disk drive, a flash memory, a read-only memory (ROM), acompact disk (CD), a digital versatile disk (DVD), a cache, arandom-access memory (RAM) and/or any other storage device or storagedisk in which information is stored for any duration (e.g., for extendedtime periods, permanently, for brief instances, for temporarilybuffering, and/or for caching of the information). As used herein, theterm tangible computer readable storage medium is expressly defined toinclude any type of computer readable storage device and/or storage diskand to exclude propagating signals and to exclude transmission media. Asused herein, “tangible computer readable storage medium” and “tangiblemachine readable storage medium” are used interchangeably. Additionallyor alternatively, the example process of FIG. 6 may be implemented usingcoded instructions (e.g., computer and/or machine readable instructions)stored on a non-transitory computer and/or machine readable medium suchas a hard disk drive, a flash memory, a read-only memory, a compactdisk, a digital versatile disk, a cache, a random-access memory and/orany other storage device or storage disk in which information is storedfor any duration (e.g., for extended time periods, permanently, forbrief instances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term non-transitory computer readablemedium is expressly defined to include any type of computer readablestorage device and/or storage disk and to exclude propagating signalsand to exclude transmission media. As used herein, when the phrase “atleast” is used as the transition term in a preamble of a claim, it isopen-ended in the same manner as the term “comprising” is open ended.

FIG. 6 depicts an example flow diagram representative of an examplemethod 600 that may be implemented to fabricate a droplet actuator viaoperation of the first, second, and third example assemblies 100, 300,400. The example method 600 may be implemented by advancing a web of abase substrate via rollers (block 602). For example, the first, second,and third rollers 102, 104, 106 may unwind and drive the base substrateor web 108 of FIG. 1 through the rollers. In some examples, the rollers102, 104, 106 are controlled by the roller drivers(s) 504 of FIG. 5. Theexample method 600 also includes ablating an electrode array on the basesubstrate (block 604). For example, the base substrate 108 may pass, viathe rollers, to the laser ablation station 114 of FIG. 1. The laser beam124 penetrates the base substrate 108 (e.g., the conductive second layer112) to selectively remove, or ablate, material from the base substrate108 to form an electrode array 126. The laser beam 124 may be controlledby the laser driver(s) 510 of FIG. 5.

The example method 600 also includes applying a hydrophobic and/ordielectric material to the electrode array (block 606). In the examplemethod 600, the hydrophobic and/or dielectric material can be ahydrophobic material such as Teflon®, a dielectric, or a combinationthereof. In some examples of the example method 600, the printer 128 ofFIG. 1 applies the hydrophobic and/or dielectric material to theelectrode array 126 of the base substrate 108. In the example method600, the hydrophobic and/or dielectric material substantially completelycovers, or insulates, the electrode array 126. In some examples, theprinter 128 is controlled by the printer driver(s) 514 of FIG. 5.

In the example method 600, the hydrophobic and/or dielectric material istreated (e.g., cured or otherwise modified), to form a treated layer onthe base substrate (block 608). For example, heat and/or an ultravioletlight is applied to the base substrate to harden the hydrophobicmaterial. The heat and/or the ultraviolet light can be applied via thecuring station 134 of FIG. 1. In some examples, curing station driver(s)520 of FIG. 5 control the curing station 134.

After treating the hydrophobic and/or dielectric material, the basesubstrate is ready for implementation as a bottom substrate of a dropletactuator. In the example method 600, a top substrate (e.g. a substrateweb) is concurrently processed for implementation as a top substrate ofthe droplet actuator. In other examples of the example method 600, thetop substrate is processed at a different time than the bottomsubstrate.

To prepare the top substrate for implementation as part of a dropletactuator in association with the base substrate, the example method 600includes advancing the top substrate via rollers (block 610). In someexamples, the first, second, and third rollers 302, 304, 306 of FIG. 3unwind and drive the top substrate 308 through the second exampleassembly 300. Also, in some examples, the rollers 302, 304, 306 arecontrolled by the roller driver(s) 504.

The example method 600 includes a decision whether to create anelectrode array on the top substrate (block 612). The top substrate caninclude a single electrode (e.g., a continuous layer of conductivematerial), an electrode array (e.g., a pattern including a plurality ofelectrodes), or a non-conductive material. If a decision is made atblock 612 to create an electrode array on the top substrate, the examplemethod 600 proceeds to block 614, where an electrode array is created onthe top substrate (e.g., the conductive second layer 312 of the topsubstrate 308) via laser ablation. The laser ablation of the topsubstrate is performed in the substantially the same manner as theablation of the base substrate at block 604 (e.g., via a laser toselectively remove conductive material in accordance with an electrodepattern).

If a decision is made not to create an electrode array on the topsubstrate (block 612), the example method 600 continues where ahydrophobic and/or dielectric material is applied to the top substrate(block 616). Also, in examples where an electrode array is formed on thetop substrate (block 614), the example method 600 proceeds to block 616.In both instances, at least a portion of the top substrate is coatedwith the hydrophobic and/or dielectric material to, for example,insulate a single electrode or the electrode array associated with thetop substrate. For example, the hydrophobic printer 314 of FIG. 3 maydeposit a hydrophobic and/or dielectric material on the top substrate.In some examples, the printer 314 is controlled via the printer driversof FIG. 5.

In the example method 600, the hydrophobic and/or dielectric materialapplied to the top substrate is treated (block 618). Treating thehydrophobic and/or dielectric material on the top substrate may beperformed substantially as described in connection with respect totreating the hydrophobic and/or dielectric material of the basesubstrate at block 608 (e.g., via heat and/or ultraviolet light appliedvia the curing station 320 of FIG. 3 and controlled by the curingstation driver(s) 520 of FIG. 5).

In the example method 600, the top substrate is processed forimplementation as part of a droplet actuator in connection with the basesubstrate. To form the droplet actuator, the example method 600 includesaligning the base substrate and the top substrate (block 620). In someexamples, the base substrate and the top substrate are configured asindividual rolls (e.g., via the respective rollers of the first andsecond example assemblies 100, 300 after the curing at blocks 608 and618). In such examples, aligning the base substrate and the topsubstrate includes aligning the individual rolls or aligning discreteportions of the base substrate and the top substrate if, for example,the individual rolls have been diced into discrete portionscorresponding to predetermined dimensions of the droplet actuator (seeblock 624). In other examples, aligning the base substrate and the topsubstrate is accomplished as part of continued advancement of the basesubstrate and top substrate via rollers such that the base substrate andthe top substrate are merged and bonded prior to dicing (e.g., asdescribed in connection with the third example process 400 of FIG. 4).The base substrate and the top substrate may be bonded via an adhesiveapplied at the bonding station 414 of FIG. 4.

Whether the alignment of the base substrate and the top substrate (e.g.,the base substrate web and the top substrate web) occurs via alignmentof discrete rolls and/or portions or as part of a roll-to-roll process(block 620), the example method 600 includes forming a gap between thebase substrate and the top substrate (block 622). In the example method600, the gap can be formed by, for example, the insertion of capillarytubes between the substrates, embossing, and/or lamination of thehydrophobic and/or dielectric surfaces of the substrates.

The example method 600 includes dicing the substrate webs intoindividual units (block 624). In some examples, the dicing occurs aspart of the roll-to-roll process such that the bonded base substrate andtop substrate are cut into an individual unit including the basesubstrate, the top substrate, and the gap. In examples where the basesubstrate and the top substrate are rolled into individual rolls (e.g.,after the respective first and second example processes 100, 300), thesubstrates are cut into discrete units separately to form the dropletactuator and to subsequently undergo bonding and gap formation (e.g.,blocks 620, 622). In the example method 600, the substrate(s) may cutvia a cutting or splitting instrument at the dicing station 416 of FIG.4. At the end of the example method 600 (block 626), the dropletactuator can receive a droplet on the hydrophobic and/or dielectricsurfaces of the substrates via the gap for manipulation by electricalpotentials delivered via the base substrate and/or the top substrate.

FIG. 7 is a block diagram of an example processor platform 700 capableof executing the instructions of FIG. 6 to implement the apparatusand/or system of FIGS. 1 and 3-5. The processor platform 700 can be, forexample, a server, a personal computer, a mobile device (e.g., a cellphone, a smart phone, a tablet such as an iPad™), a personal digitalassistant (PDA), an Internet appliance, or any other type of computingdevice.

The processor platform 700 of the illustrated example includes aprocessor 712. The processor 712 of the illustrated example is hardware.For example, the processor 712 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors or controllers fromany desired family or manufacturer.

The processor 712 of the illustrated example includes a local memory 713(e.g., a cache). The processor 712 of the illustrated example is incommunication with a main memory including a volatile memory 714 and anon-volatile memory 716 via a bus 718. The volatile memory 714 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM)and/or any other type of random access memory device. The non-volatilememory 716 may be implemented by flash memory and/or any other desiredtype of memory device. Access to the main memory 714, 716 is controlledby a memory controller.

The processor platform 700 of the illustrated example also includes aninterface circuit 720. The interface circuit 720 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 722 are connectedto the interface circuit 720. The input device(s) 722 permit(s) a userto enter data and commands into the processor 712. The input device(s)can be implemented by, for example, an audio sensor, a microphone, acamera (still or video), a keyboard, a button, a mouse, a touchscreen, atrack-pad, a trackball, isopoint and/or a voice recognition system.

One or more output devices 724 are also connected to the interfacecircuit 720 of the illustrated example. The output devices 724 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a light emitting diode (LED), a printer and/or speakers).The interface circuit 720 of the illustrated example, thus, typicallyincludes a graphics driver card, a graphics driver chip or a graphicsdriver processor.

The interface circuit 720 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network726 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 700 of the illustrated example also includes oneor more mass storage devices 728 for storing software and/or data.Examples of such mass storage devices 728 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAIDsystems, and digital versatile disk (DVD) drives.

The coded instructions 732 of FIG. 7 may be stored in the mass storagedevice 728, in the volatile memory 714, in the non-volatile memory 716,and/or on a removable tangible computer readable storage medium such asa CD or DVD.

From the foregoing, it will be appreciated that the above disclosedmethods, systems, and apparatus provide for fabrication of dropletactuators via laser ablation and roll-to-roll processing to efficientlyproduce substrates that form the droplet actuators without comprisingtechnical superiority of the electrodes associated with the dropletactuators. A base substrate is efficiently moved through stations viarollers without interruption to create electrode arrays, coat the arrayswith a hydrophobic material, and cure the hydrophobic material to createa substrate that can serve as a structural support for a dropletdisposed on the droplet actuator. Further, processing of the topsubstrate of the droplet actuator can be achieved using substantiallythe same roll-to-roll techniques, with additional customization as towhether, for example, the top substrate includes an electrode array. Theroll-to-roll processing provides for individually wound rolls of theprocessed base substrate and top substrate that can be further diced andaligned to create individual droplet actuators. Alternatively,roll-to-roll processing may be further used to merge the base substrateand the top substrate to create a single roll that can be diced.

The examples disclosed herein utilize laser ablation to define electrodearrays on the substrates as the substrates are driven by the rollers.Laser ablation provides for electrode arrays having high performancequalities without impacting production speeds. By exposing successiveportions of the substrates to a laser, the electrode patterns arecreated on the substrates in accordance with the rate at which therollers advance the substrates. Low operational costs are achieved as aresult of the thin layers of pre-adhered conductive and non-conductivematerials to form the base substrate. Such a configuration reduces (1)material costs as compared to thick-film printing methods, and (2) thenumber of processing steps due to the pre-adhesion of the substratesprior to formation of the electrode patterns. The electricalconductivity, electrode inter-digitization, low surface and edgeroughness, and high resolution, and small footprint of the electrodearrays achieved via laser ablation improves the precision of the dropletmanipulation performed via resulting droplet actuator. Further, insubstantially completely insulating the electrodes of the substrates,the example methods disclosed herein prevent unintended chemical changesor reactions to the droplet placed on the hydrophobic materials duringmanipulation of the droplet via electrical potentials.

Thus, the substrates are processed through the stations in asubstantially implementation-ready state such that the processedsubstrates can be diced into discrete portions after the curing of thehydrophobic materials to create one or more droplet actuators. Such areduction in processing the substrates improves production time andlowers costs without compromising the quality of the resulting dropletactuators.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. A non-transitory computer readable mediumcomprising instructions that, when executed, cause at least oneprocessor to at least: control movement of a laser to cause the laser toetch an electrode pattern in a first substrate, the electrode patternincluding a first set of electrodes, a second set of electrodes, and athird set of electrodes, each of the first set of electrodes, the secondset of electrodes, and the third set of electrodes spaced apart fromeach other, the second set of electrodes disposed between the first setof electrodes and the third set of electrodes; control a printer driverto cause a hydrophobic material and a dielectric material to be appliedto the second set of electrodes and not the first set of electrodes viaa printer; control a bonding driver to cause a gap to be defined betweenthe first substrate and a second substrate; and control a dicing driverto cause a portion the first substrate and a portion of the secondsubstrate to be cut into a droplet actuator, the droplet actuatorincluding the first, second, and third sets of electrodes, the first setof electrodes and the third set of electrodes disposed proximate torespective edges of the portion of the first substrate defining thedroplet actuator.
 2. The non-transitory computer readable medium ofclaim 1, wherein the instructions, when executed, cause the at least oneprocessor to control the movement of the laser to generate the electrodepattern using spacings defined between lines, the spacings having awidth of less than 10 micrometers.
 3. The non-transitory computerreadable medium of claim 1, wherein the instructions, when executed,cause the at least one processor to: control the roller driver to causea first portion of the first substrate including the first set ofelectrodes to be moved away from the printer; and control a rollerdriver to cause a second portion of the first substrate including thesecond set of electrodes to be positioned relative to the printer forapplication of the hydrophobic material and the dielectric material. 4.The non-transitory computer readable medium of claim 1, wherein theinstructions, when executed, cause the at least one processor to controlthe bonding driver to cause one or more projections to be at leastpartially inserted into the gap.
 5. An apparatus comprising: memory; andat least one processor to: cause a laser to pattern a first electrodepattern on a first portion of a first substrate, the first electrodepattern including a first set of electrodes and a second set ofelectrodes; cause the laser to pattern a second electrode pattern on asecond portion of the first substrate, the first portion spaced apartfrom the second portion; cause a printer to apply a hydrophobic materialand a dielectric material to the first set of electrodes during thepatterning of the second electrode pattern on the second portion of thefirst substrate; cause rollers to move the second set of electrodes awayfrom the printer during the patterning of the second electrode patternon the second portion of the first substrate; cause the rollers to alignthe first substrate with a second substrate; and cause a bonding driverto insert a frame between the first substrate and the second substrateto form a gap therebetween to receive a droplet.
 6. The apparatus ofclaim 5, wherein the frame includes one or more projections at leastpartially disposed in the gap.
 7. The apparatus of claim 5, wherein thefirst set of electrodes includes lines having at least partially curvededges defining spacings between the lines.
 8. The apparatus of claim 5,wherein the at least one processor is to cause the laser to pattern athird electrode pattern on the second substrate, at least one of thefirst electrode pattern or the second electrode pattern to be alignedwith the third electrode pattern.
 9. The apparatus of claim 5, whereinthe at least one processor is to cause the printer to apply thedielectric material in combination with the hydrophobic material to thefirst set of electrodes.
 10. A method for making a droplet actuator, themethod comprising: ablating a first substrate with a laser to form anelectrode array on the first substrate; applying at least one of ahydrophobic material or a dielectric material to at least a portion ofthe electrode array to form a first treated layer on the firstsubstrate; and aligning the first substrate with a second substrate, thesecond substrate including a second treated layer, wherein the alignmentincludes a gap between at least a portion of the first treated layer andat least a portion of the second treated layer; and inserting one ormore projections at least partially in the gap, the one or moreprojections including capillaries.
 11. The method of claim 10, whereinthe electrode array includes spacings having a width of less than 10micrometers.
 12. The method of claim 10, wherein the first substrateincludes a conductive layer and a non-conductive layer and whereinablating the first substrate includes: projecting a pattern onto aportion of the first substrate via a lens; and focusing the laser on theportion, wherein the laser is to penetrate the conductive layer and thenon-conductive layer.
 13. The method of claim 10, wherein ablating thefirst substrate further includes exposing a first portion of the firstsubstrate and a second portion of the second substrate to the laser insuccession, the laser to form the electrode array on the first portionand the second portion.
 14. The method of claim 13, further includingcoating the first portion of the first substrate with the hydrophobicmaterial and the dielectric material at substantially the same time asthe second portion of the first substrate is exposed to the laser. 15.The method of claim 13, further including dicing the first substrate andthe second substrate to form a first droplet actuator including thefirst portion of the first substrate and a second droplet actuatorincluding the second portion of the first substrate.
 16. The method ofclaim 10, further including bonding a first portion of the firstsubstrate and a second portion of the second substrate with an adhesivematerial, the bonding to maintain the gap.
 17. The method of claim 10,wherein the electrode array is a first electrode array and furtherincluding forming a second electrode array on the second substrate. 18.The method of claim 10, wherein the ablating includes etching theelectrode array via movement of the laser.
 19. The method of claim 10,wherein the second substrate includes a non-conductive material.